<template>
  <div class="s-canvas">
    <canvas
      id="s-canvas"
      :width="contentWidth"
      :height="contentHeight"
    ></canvas>
  </div>
</template>

<script lang="ts">
import { defineComponent, onMounted, watch } from "vue";

export default defineComponent({
  name: "Identify",
  props: {
    identifyCode: {
      type: String,
      default: "1234"
    },
    fontSizeMin: {
      type: Number,
      default: 18
    },
    fontSizeMax: {
      type: Number,
      default: 24
    },
    backgroundColorMin: {
      type: Number,
      default: 120
    },
    backgroundColorMax: {
      type: Number,
      default: 240
    },
    backgroundColor: {
      type: String
    },
    colorMin: {
      type: Number,
      default: 100
    },
    colorMax: {
      type: Number,
      default: 200
    },
    drawLine: {
      type: Boolean,
      default: true
    },
    lineColorMin: {
      type: Number,
      default: 40
    },
    lineColorMax: {
      type: Number,
      default: 180
    },
    drawDot: {
      type: Boolean,
      default: true
    },
    dotColorMin: {
      type: Number,
      default: 0
    },
    dotColorMax: {
      type: Number,
      default: 255
    },
    contentWidth: {
      type: Number,
      default: 112
    },
    contentHeight: {
      type: Number,
      default: 38
    }
  },
  setup(props) {
    // 生成一个随机数
    const randomNum = (min, max) => {
      return Math.floor(Math.random() * (max - min) + min);
    };
    // 生成一个随机的颜色
    const randomColor = (min, max) => {
      let r = randomNum(min, max);
      let g = randomNum(min, max);
      let b = randomNum(min, max);
      return "rgb(" + r + "," + g + "," + b + ")";
    };
    const drawPic = () => {
      let canvas = document.getElementById("s-canvas");
      let ctx = (canvas as any).getContext("2d");
      ctx.textBaseline = "bottom";
      // 绘制背景
      ctx.fillStyle =
        props.backgroundColor ||
        randomColor(props.backgroundColorMin, props.backgroundColorMax);
      ctx.fillRect(0, 0, props.contentWidth, props.contentHeight);
      // 绘制文字
      for (let i = 0; i < props.identifyCode.length; i++) {
        drawText(ctx, props.identifyCode[i], i);
      }
      props.drawLine && drawLine(ctx);
      props.drawDot && drawDot(ctx);
    };

    const drawText = (ctx, txt, i) => {
      ctx.fillStyle = randomColor(props.colorMin, props.colorMax);
      ctx.font = randomNum(props.fontSizeMin, props.fontSizeMax) + "px SimHei";
      let x = (i + 1) * (props.contentWidth / (props.identifyCode.length + 1));
      let y = randomNum(props.fontSizeMax, props.contentHeight - 5);
      var deg = randomNum(-20, 20);
      // 修改坐标原点和旋转角度
      ctx.translate(x, y);
      ctx.rotate((deg * Math.PI) / 180);
      ctx.fillText(txt, 0, 0);
      // 恢复坐标原点和旋转角度
      ctx.rotate((-deg * Math.PI) / 180);
      ctx.translate(-x, -y);
    };
    const drawLine = ctx => {
      // 绘制干扰线
      for (let i = 0; i < 4; i++) {
        ctx.strokeStyle = randomColor(props.lineColorMin, props.lineColorMax);
        ctx.beginPath();
        ctx.moveTo(
          randomNum(0, props.contentWidth),
          randomNum(0, props.contentHeight)
        );
        ctx.lineTo(
          randomNum(0, props.contentWidth),
          randomNum(0, props.contentHeight)
        );
        ctx.stroke();
      }
    };
    const drawDot = ctx => {
      // 绘制干扰点
      for (let i = 0; i < 100; i++) {
        ctx.fillStyle = randomColor(0, 255);
        ctx.beginPath();
        ctx.arc(
          randomNum(0, props.contentWidth),
          randomNum(0, props.contentHeight),
          1,
          0,
          2 * Math.PI
        );
        ctx.fill();
      }
    };

    watch(
      () => props.identifyCode,
      () => {
        drawPic();
      }
    );

    onMounted(() => {
      drawPic();
    });

    return {
      drawPic
    };
  }
});
</script>
